Make SkPngCodec decode progressively.

dm/DMSrcSink.cpp

Index: dm/DMSrcSink.cpp
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index 18ac6b420a70a0661af55c7a2a3fb15255072ea1..67cc3edff2fb2bc2c7523d1319c29a090fec41bc 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -434,32 +434,49 @@ Error CodecSrc::draw(SkCanvas* canvas) const {
             break;
         }
         case kScanline_Mode: {
-            if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, NULL, colorPtr,
-                                                                colorCountPtr)) {
-                return "Could not start scanline decoder";
-            }
+            const bool supportsNewScanlineDecoding = fPath.endsWith("png");
+            if (supportsNewScanlineDecoding) {
+                if (SkCodec::kSuccess != codec->startIncrementalDecode(decodeInfo,
+                        nullptr, colorPtr, colorCountPtr)) {
+                    return "Could not start incremental decode";
+                }
+                int rowsDecoded;
+                if (SkCodec::kIncompleteInput == codec->incrementalDecode(
+                        [&bitmap](int rowNum) -> void* {
+                            return bitmap.getAddr(0, rowNum);
+                        }, &rowsDecoded)) {
+                    codec->fillIncompleteImage(decodeInfo, bitmap.getPixels(), bitmap.rowBytes(),
+                                               SkCodec::kNo_ZeroInitialized, decodeInfo.height(),
+                                               rowsDecoded);
+                }
 
-            void* dst = bitmap.getAddr(0, 0);
-            size_t rowBytes = bitmap.rowBytes();
-            uint32_t height = decodeInfo.height();
-            switch (codec->getScanlineOrder()) {
-                case SkCodec::kTopDown_SkScanlineOrder:
-                case SkCodec::kBottomUp_SkScanlineOrder:
-                case SkCodec::kNone_SkScanlineOrder:
-                    // We do not need to check the return value.  On an incomplete
-                    // image, memory will be filled with a default value.
-                    codec->getScanlines(dst, height, rowBytes);
-                    break;
-                case SkCodec::kOutOfOrder_SkScanlineOrder: {
-                    for (int y = 0; y < decodeInfo.height(); y++) {
-                        int dstY = codec->outputScanline(y);
-                        void* dstPtr = bitmap.getAddr(0, dstY);
-                        // We complete the loop, even if this call begins to fail
-                        // due to an incomplete image.  This ensures any uninitialized
-                        // memory will be filled with the proper value.
-                        codec->getScanlines(dstPtr, 1, bitmap.rowBytes());
+            } else {
+                if (SkCodec::kSuccess != codec->startScanlineDecode(decodeInfo, NULL, colorPtr,
+                                                                    colorCountPtr)) {
+                    return "Could not start scanline decoder";
+                }
+
+                void* dst = bitmap.getAddr(0, 0);
+                size_t rowBytes = bitmap.rowBytes();
+                uint32_t height = decodeInfo.height();
+                switch (codec->getScanlineOrder()) {
+                    case SkCodec::kTopDown_SkScanlineOrder:
+                    case SkCodec::kBottomUp_SkScanlineOrder:
+                        // We do not need to check the return value.  On an incomplete
+                        // image, memory will be filled with a default value.
+                        codec->getScanlines(dst, height, rowBytes);
+                        break;
+                    case SkCodec::kOutOfOrder_SkScanlineOrder: {
+                        for (int y = 0; y < decodeInfo.height(); y++) {
+                            int dstY = codec->outputScanline(y);
+                            void* dstPtr = bitmap.getAddr(0, dstY);
+                            // We complete the loop, even if this call begins to fail
+                            // due to an incomplete image.  This ensures any uninitialized
+                            // memory will be filled with the proper value.
+                            codec->getScanlines(dstPtr, 1, bitmap.rowBytes());
+                        }
+                        break;
                     }
-                    break;
                 }
             }